The present invention relates to cutting tables for supporting metal workpieces to be cut by a torch or the like.
Cutting tables are frequently used for performing cutting operations on metal workpieces using a cutting device such as a gas torch, laser, or the like. A cutting table generally includes a table that supports the workpiece, and a cutting device that is moved by a suitable drive system to guide the cutting device along predetermined paths as the cutting device is operated to cut the workpiece. The drive system can be computer-controlled for guiding the cutting device's movement. The table includes openings through which molten slag formed during the cutting process falls into a space below the table. The table usually includes a duct system below the table for drawing away smoke and fumes created during the cutting process. Accordingly, such cutting tables are often referred to as “downdraft cutting tables” or the like.
The molten slag tends to build up below the table, and must be removed in order to keep the table in proper operating condition. Various slag-removal systems have been developed or proposed for removing slag from beneath cutting tables either continuously or periodically. Many slag-removable systems employ some type of scraper or plow that is scraped along the floor beneath the table for scraping off the slag that has fallen onto the floor. The slag is pushed to a location from which the slag can be collected and disposed of. The plow typically must then be reversed in direction to move it back to its starting point in preparation for another slag-removal cycle. The drive system for moving the plow thus requires limit switches or the like for detecting when the plow has reached the end of one slag-removal pass, and for detecting when the plow has reached the starting point during the reverse movement. Additionally, the motor of the drive system must be reversible (or a reversing gear arrangement must be employed) in order to move the plow back to the starting point.
As an alternative to a periodic type of slag-removal system as described above, a continuously operable conveyor can be disposed below the table for catching the slag as it falls through the table and for carrying the slag away to a location from which the slag can be collected and disposed of. However, a drawback of such a continuous conveyor system is that the conveyor can be damaged by the molten or hot slag when it falls onto the conveyor.
The duct system of existing downdraft cutting tables generally includes one or more ducts that extend longitudinally (i.e., parallel to the direction along which the slag plow moves) beneath the table. Each duct may include openings that are spaced apart along the longitudinal direction, and each opening may include a damper or door that is movable between open and closed positions. The opening and closing of the doors in some cases is dependent on the movement of the slag-removal device beneath the table.